Surface shape recognition sensor and method of manufacturing the same

ABSTRACT

A surface shape recognition sensor of this invention has a surface protective film having a hydrophobic property on an insulating protective film which is made of an insulator and formed to cover a sensor electrode, and includes at least a ground electrode which is formed on the substrate such that the ground electrode is partly exposed on the surfaces of the insulating protective film and surface protective film so as to be insulated/isolated from the sensor electrode and come into contact with the surface of a detection target. This sensor prevents fingerprint residues from easily remaining and improves tamper resistance.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a surface shape recognitionsensor used to sense a surface shape having fine recesses andprojections such as human fingerprints and animal's noseprints and amethod of manufacturing the sensor and, more particularly, to a surfaceshape recognition sensor whose recognition surface is protected and amethod of manufacturing the sensor.

[0002] With the recent proliferation of the Internet, a great deal ofattention has been paid to the importance of authentication. Biometrics,in which authentication is performed by measuring/evaluating biologicalcharacteristics, has greatly advanced as a technical field ofauthentication. Authentication using fingerprints, in particular, hasbeen vigorously studied as an authentication means formeasuring/evaluating a physical characteristic that cannot be easilychanged. In order to perform authentication by using a fingerprint, thefingerprint is read. Systems for reading fingerprints include varioussystems such as optical systems and capacitive systems. Except for someof the optical systems, when a fingerprint is to be read, the fingergenerally touches a fingerprint sensor surface.

[0003] In a system in which the fingers are made to touch a fingerprintsensor surface, fingerprint residues including sebum remain on thesensor. With the recent increasing orientation toward cleanliness, manyusers hate to touch the sensor surface, and hence it is required to takemeasures against this problem (e.g., fourth-page article of the thirdevening edition of the Asahi Shimbun published by Tokyosha, Aug. 22,1999). In addition, a fingerprint shape can be easily collected andreproduced from a fingerprint residue left on the sensor surface by theso-called powder method using aluminum powder like that executed by acrime laboratory. From the viewpoint of tamper resistance as well, it isnecessary to take measures against the problem.

[0004] Furthermore, fingerprint residues interfere as noise withauthentication, and hence degrade the authentication performance of thefingerprint sensor. Under the present circumstances, cleaning and wipingthe sensor surface are only measures against these problems. With suchmeasures, however, for example, the sensor cannot be continuously used,thus prosing a serious problem.

SUMMARY OF THE INVENTION

[0005] It is, therefore, the main object of the present invention tosuppress a deterioration in cleanliness on the detection surface of asurface shape recognition sensor such as a fingerprint sensor used for,for example, authentication due to residues such as fingerprint residuesleft on the detection surface which a detection target such as a fingertouches, and prevent fingerprint residues from easily remaining, therebyimproving tamper resistance and suppressing a deterioration in detectionprecision with respect to a surface shape such as a fingerprint.

[0006] In order to achieve the above object, according to one aspect ofthe present invention, there is provided a surface shape recognitionsensor comprising a plurality of sensor electrodes arranged in the sameplane on a substrate so as to be insulated/isolated from each other, aninsulating protective film which is made of an insulator and formed tocover the sensor electrodes, capacitance detection means for detecting acapacitance formed by the sensor electrode, a surface protective filmwhich has a hydrophobic property and is formed on the insulatingprotective film, and a ground electrode which is formed on the substratesuch that the ground electrode is partly exposed on surfaces of theinsulating protective film and the surface protective film so as to beinsulated/isolated from the sensor electrode and come into contact witha surface of a detection target, wherein the capacitance detection meansis configured to detect a capacitance between the ground electrode andeach of the sensor electrodes.

[0007] This arrangement restrains substances existing on the surface ofa detection target from remaining on the surface of the surfaceprotective film upon contact of the detection target with the surfaceprotective film.

[0008] According to another aspect of the present invention, there isprovided a method of manufacturing a surface shape recognition sensorincluding at least a plurality of sensor electrodes arranged in the sameplane on a substrate so as to be insulated/isolated from each other, aninsulating protective film which is made of an insulator and formed tocover the sensor electrodes, capacitance detection means for detecting acapacitance formed by the sensor electrode, and a connection terminalexposed on a surface of the insulating protective film, wherein asurface protective film made of a specific material, which forms a filmhaving a hydrophobic property, is formed on the insulating protectivefilm by coating the film with a coating solution in which the specificmaterial is dissolved.

[0009] By manufacturing the sensor in this manner, a surface protectivefilm is not easily formed on the upper surface (exposed surface) of aconnection terminal made of gold or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1A is a schematic sectional view showing part of thestructure of a surface shape recognition sensor according to the firstembodiment of the present invention;

[0011]FIG. 1B is a plan view showing part of the structure of thesurface shape recognition sensor according to the first embodiment ofthe present invention;

[0012]FIG. 1C is a schematic sectional view showing part of thestructure of the surface shape recognition sensor according to the firstembodiment of the present invention;

[0013]FIG. 2 is a schematic sectional view showing part of the structureof the surface shape recognition sensor according to the firstembodiment of the present invention;

[0014]FIG. 3 is a schematic sectional view showing part of the structureof a surface shape recognition sensor according to the second embodimentof the present invention;

[0015]FIG. 4 is a schematic sectional view showing part of the structureof the surface shape recognition sensor according to the secondembodiment of the present invention;

[0016]FIG. 5A is a sectional view for explaining a step in a method ofmanufacturing a surface shape recognition sensor according to the thirdembodiment of the present invention;

[0017]FIG. 5B is a sectional view for explaining a step following thestep in FIG. 5A in the method of manufacturing a surface shaperecognition sensor according to the third embodiment of the presentinvention;

[0018]FIG. 5C is a sectional view for explaining a step following thestep in FIG. 5B in the method of manufacturing a surface shaperecognition sensor according to the third embodiment of the presentinvention;

[0019]FIG. 6 is a schematic sectional view showing another region of thesurface shape recognition sensor shown in FIG. 5C; and

[0020]FIG. 7 is a plan view showing the structure of the surface shaperecognition sensor shown in FIG. 5C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The embodiments of the present invention will be described indetail below with reference to the accompanying drawings.

[0022] [First Embodiment]

[0023] The first embodiment of the present invention will be describedfirst. FIGS. 1A, 1B, and 1C explain a method of manufacturing a surfaceshape recognition sensor (sensor chip) according to this embodiment. Thestate shown in FIG. 1A will be described first. First of all, amultilevel interconnection layer 102 is formed on a semiconductorsubstrate 101 made of, for example, silicon. The uppermost layer of themultilevel interconnection layer 102 is covered with an insulating film103, and interconnections 104 and 105 are formed on the insulating film103.

[0024] The multilevel interconnection layer 102 is formed from aplurality of elements such as MOS transistors (not shown) and aplurality of interconnections (not shown) which connect the elements,and forms a sensor circuit 115 and the like. The interconnections 104and 105 are connected to these circuits. Note that an illustration ofthe sensor circuit 115 is omitted in subsequent drawings, e.g., FIGS.1C, 3, and 4.

[0025] The interconnections 104 and 105 are covered with an interlayerdielectric film 108. Connection electrodes 106 and 107 extending throughthe through holes formed in portions of the interlayer dielectric film108 are connected to the interconnections 104 and 105. The respectiveinterconnections and connection electrodes may be formed by patterningusing a known film forming technique, photolithographic technique, oretching technique. An insulating film 109 is formed on the interlayerdielectric film 108 such that the central portions of the upper portionsof the connection electrodes 106 and 107 are exposed.

[0026] In this state, a copper film having a thickness of about 0.1 μmis formed on the insulating film 109 and the exposed portions of theconnection electrodes 106 and 107 by, for example, sputtering. A resistpattern having an opening portion with a square shape in plan which iscentered on the connection electrode 106 is formed on the connectionelectrode 106 and insulating film 109. A gold film having a thickness ofabout 1 μm is formed on the copper film exposed in this opening portionby electrolytic plating or the like.

[0027] The above resist pattern is removed, and a new resist patternhaving opening portions in a lattice pattern is formed on the pluralityof connection electrodes 107, and a gold film having a thickness ofabout 3 μm is formed on the copper film exposed in the lattice patternby electrolytic plating or the like. The resist pattern is then removed.

[0028] With this process, a gold pattern with a square shape in plan isformed on the upper portion of the connection electrode 106, and a goldlattice pattern is continuously formed on the upper portions of theplurality of connection electrodes 107. The lower copper film is removedby etching using the gold pattern formed in this manner as a mask,thereby electrically isolating the lattice pattern portion from theportion with a square shape in plan.

[0029] As a result, a square sensor electrode 111 connected to theconnection electrode 106 is formed on the insulating film 109, and aground electrode 112 connected to the connection electrodes 107 isformed.

[0030] As shown in FIG. 1B, sensor electrodes 111 are so formed as to beisolated from each other on the sensor chip, and the ground electrode112 in a lattice pattern is formed such that the sensor electrodes 111are arranged in squares.

[0031] When the sensor electrodes 111 and ground electrode 112 areformed in the above manner, an insulating protective film 113 serving asa capacitance film is formed on the sensor electrode 111, as shown inFIG. 1C. The insulating protective film 113 is formed such that thesensor electrode 111 is covered with the film but the upper portion ofthe ground electrode 112 is exposed. For example, the insulatingprotective film 113 can be formed by forming a polyimide film made of apolyimide material included in CRC-8300 series available from SUMITOMOBAKELITE to a thickness of about 3 μm by a coating technique and settingthe film by heating it at about 300° C.

[0032] After the insulating protective film 113 is formed in thismanner, a fluoroplastic film (surface protective film) 114 made of afluorocarbon material (specific material) is formed on the insulatingprotective film 113. As a fluorocarbon material, for example, AF 1600(Teflon®) available from DuPont can be used.

[0033] A method of forming the fluoroplastic film 114 will be describedbelow. First of all, AF 1600 is dissolved in Fluorinert FC-75 (solvent)available from 3M to form a saturated solution of AF 1600 at a roomtemperature of 23.5° C. This saturated solution will be referred to as aTeflon® saturated solution hereinafter.

[0034] When a saturated solution is formed in the above manner, thissaturated solution is applied onto the insulating protective film 113 byspin coating. The resultant structure is heated in an atmosphere at 170°C. for 5 min. The resultant structure is then annealed in a nitrogenatmosphere at 300° C. for 1 hr. As a result, the fluoroplastic film 114can be formed, as shown in FIG. 1C. At this time, as will be describedlater, since a coating film of a fluoroplastic film is thin and exhibitspoor adhesion on gold, the fluoroplastic film 114 is hardly formed onthe ground electrode 112 made of gold.

[0035] Note that a plurality of sensor chips (surface shape recognitionsensors) are simultaneously formed on the semiconductor substrate 101which is a semiconductor wafer, detection surfaces formed from theplurality of sensor electrodes 111 are formed on the respective sensorchips, and the detection surfaces are protected by the insulatingprotective film 113 and fluoroplastic film 114. FIG. 1C shows some ofthese components, i.e., schematically shows part of the structure of thesurface shape recognition sensor. The sensor circuit 115 shown in FIG. 1is connected to the sensor electrode 111 through the interconnection 104and connection electrode 106, and is also connected to the groundelectrode 112 through the interconnections 105 and connection electrodes107.

[0036] Various types of connection terminals are formed on the surfaceof the sensor chip. For example, the ground electrode 112 is formed on adetection surface, and an external connection terminal is formed on anouter peripheral portion of the sensor chip. In this state, when afluoroplastic film is formed by only spin coating as described above,the above connection terminals are also covered with the fluoroplasticfilm. A fluoroplastic film formed on connection terminals will bedescribed below.

[0037] First of all, the following samples were formed. A coatingsolution obtained by mixing a Teflon® saturated solution with FluorinertFC-75 (solvent) at a mixing ratio of 3:1 or 1:1 was applied onto asubstrate with each of underlayers in various states by spin coating at1,000 rmp. The resultant structure was heated in an atmosphere at 170°C. for 5 min. The resultant structure was then annealed in a nitrogenatmosphere at 300° C. for 1 hr, thereby forming a Teflon® film. Table 1shows the result of obtaining the thickness of each Teflon® film formedin this manner by in-depth analysis based on Auger electronspectroscopy. TABLE 1 Mixing ratio Underlayer 3:1 1:1 gold 1 nm or lessabout 10 nm polyimide 12 nm 200 to 300 nm silicon 12 nm 200 to 300 nmsilicon oxide film 12 nm 200 to 300 nm

[0038] As is obvious from Table 1, the coating films greatly vary inthickness at the different mixing ratios. Although the number ofrevolutions in coating is set to 1,000 rpm in Table 1, the filmthickness hardly changes even if the number of revolutions in coating ischanged between 500 to 5,000 rpm.

[0039] It is apparent from Table 1 that coating films greatly vary inthickness depending on the underlayer materials. As is obvious, inparticular, a film is not formed much on gold. Although the details of acause of such differences are not clear from a molecular or atomic pointof view, it is conjectured that such differences are based on thedifferences in wettability and surface energy between the Teflon®saturated solution and the underlayers.

[0040] When the adhesion of each formed coating film (Teflon® film) withrespect to each underlayer is performed by a Scotch tape test inaddition to the above test, the coating film formed on the goldunderlayer peels off, but the coating films on the substrates with theunderlayers made of other materials keep adhering without peeling off.It is therefore obvious that the coating film on gold is thin andexhibit poor adhesion.

[0041] It is also evident from the following experiment result that theadhesion of the Teflon® film on gold is poor. After the above Teflon®saturated solution is applied onto a substrate with a gold underlayer,the electric resistance of the substrate is measured through the coatingfilm by using a tester. In this case, a resistance can be measured inspite of the existence of the Teflon® film which is a nonconductor. Incontrast to this, when the Teflon® film is formed on a silicon substrategenerally exhibiting several kΩ, the measured resistance becomesinfinite.

[0042] These results indicate that the Teflon® film formed on gold peelsupon contact of the probe of the tester to allow intermetallicconnection with the probe. This property of the Teflon® film remainsunchanged even if the underlayer is made of stainless steel. On asubstrate with a stainless steel underlayer, only a Teflon® film withpoor adhesion can be formed. The above-described property of a Teflon®film is very effective in forming the fluoroplastic film 114 on thesurface shape recognition sensor according to this embodiment as shownin FIG. 1C, as will be described next.

[0043] A detection surface has the ground electrode 112, and forexample, static electricity generated when the finger touches thedetection surface flows in the ground electrode 112. This protectscircuit elements such as the sensor circuits 115 simultaneously formedon the semiconductor substrate 101 against electrostatic breakdown.

[0044] If the upper surface of the ground electrode 112 is covered withthe fluoroplastic film 114, the above removal of static electricitycannot be done. As described above, however, the fluoroplastic film 114is not formed on the upper surface (exposed surface) of the groundelectrode 112. According to the surface shape recognition sensor in FIG.1C, therefore, static electricity can be removed through the groundelectrode 112.

[0045] The above surface shape recognition sensor (sensor chip) has aplurality of sensor electrodes 111 arranged in the form of a matrix. Forexample, the plurality of sensor electrodes 111 are arranged at 150-μmintervals to form the detection surface of the sensor chip. As describedabove, the sensor circuit is formed below the insulating film 103 on thesemiconductor substrate 101 to detect the capacitance formed between theground electrode 112 and each sensor electrode 111. For example, sensorcircuits are prepared for the respective sensor electrodes 111, and anoutput from each sensor circuit is processed by a processing meansconstituted by other circuits (not shown). The resultant data is outputas image data obtained by converting the capacitance formed by eachsensor electrode 111 into halftone data.

[0046] For example, as shown in FIG. 2, the sensor chip includes anexternal connection electrode 211 connected, through a connectionelectrode 206, to an interconnection 204 connected to any circuit formedon the multilevel interconnection layer 102, and a bump (externalconnection terminal) 215 made of gold on the external connectionelectrode 211. This sensor chip is mounted on a mount substrate (anothersubstrate) by connecting the bump 215 to a connection portion of themount substrate.

[0047] In this case, the above output image data is output to the mountsubstrate side through the external connection electrode 211 and bump215. If, therefore, the fluoroplastic film 114 is formed on theinsulating protective film 113 by spin coating, the fluoroplastic film114 is also formed on the bump 215 formed on the sensor chip.

[0048] As described above, only a thin Teflon® film exhibiting pooradhesion can be formed on gold. Even if, therefore, the fluoroplasticfilm 114 is formed by spin coating, almost no film is formed on the bump215.

[0049] For example, a Teflon® solution obtained by diluting a Teflon®saturated solution at a mixing ratio of 1:1 is applied, by spin coatingat 1,000 rpm, to a wafer on which a plurality of sensor chips, on eachof which components up to the insulating protective film 113 are formed,are simultaneously formed. The resultant structure is heated in anatmosphere at 170° C. and annealed in a nitrogen atmosphere at 300° C.for 30 min to form Teflon® films (fluoroplastic films 114).

[0050] Even if a Teflon® film is formed in this manner, a Teflon® filmhaving a thickness of about 200 to 300 nm is formed, with good adhesion,on the insulating protective film 113 on which a plurality of sensorelectrodes 111 are arranged, but almost no Teflon® film is formed on thebump 215. Even if a Teflon® film is formed on the bump 215, the filmthickness is about 10 nm as indicated by Table 1 and the film is likelyto peel off.

[0051] Even if, therefore, the fluoroplastic film 114 is formed byapplying a Teflon® solution by spin coating, the fluoroplastic film 114on the bump 215 need not be removed separately, and each sensor chip canbe mounted on the mount substrate with electric connection beingestablished. For example, the bump 215 can be connected to an inner leadused in TAB mounting in a short period of time by an eutectic reaction.In this case, the applied temperature instantaneously reaches 420° C.,and it is expected that the thin fluoroplastic film 114 on the suturethread 214 is removed by this heat.

[0052] When a continuity test was actually conducted by bringing a testprobe pin into contact with the bumps 215 for external connection on awafer on which the plurality of sensor chips described above are formed(without cutting the wafer into chips), 80% chips were determined asdefective due to contact failures at the bumps 215. When, however, thewafer was cut into chips and TAB mounting is executed, all the chipswere determined as nondefective. This indicates that the thinfluoroplastic films 114 on the bumps 215 were removed at the time of TABmounting.

[0053] The effect of the fluoroplastic film 114 formed by coating in theabove manner will be described next. In this embodiment, the detectionsurface of the sensor chip is covered with the fluoroplastic film 114.Even if, therefore, the finger touches the detection surface, thedetection surface becomes resistant to contamination and improves intamper resistance. This effect originates from the fact that thefluoroplastic film 114 tends to repel moisture existing on the surfaceof the finger. In addition, it is conjectured that the fluoroplasticfilm 114 peels off on the molecular level. This is another factor forthe above effect.

[0054] As described above, since the fluoroplastic film 114 peels off onthe molecular level, it becomes thinner as the sensor chip is used, andeventually stops exhibiting the above effect. When a test of pressing asmall rectangular plate against the surface of a sensor chip under 1 MPawas actually conducted as a durability test on a fingerprint sensor onwhich a fluoroplastic film was formed under the above conditions, it wasconfirmed that the residual fingerprint removing effect was lost afterabout 5,000 tests. Obviously, this durability test is a kind ofaccelerated test as compared with actual finger touching, and hencesufficient durability is ensured within a practical range.

[0055] In addition, selective coating of a fluoroplastic film andfingerprint residue removing property like those described above are notlimited to the case wherein Teflon® is used. For example, even ifanother thin film having a hydrophobic property and lipophobic property,like a thin fluorocarbon film such as Cytop available from Asahi Glass,is used, the same effect as described above can be obtained. It isconjectured that this thin film also peels off by a thickness onmolecular level upon touching of the finger (detection target). It istherefore conjectured that the effect owing to peeling of the thin filmon molecular level can also be obtained.

[0056] As described above, the greatest characteristic feature of thisembodiment is that the surface of a surface shape recognition sensor canbe properly maintained by using a fluoroplastic film and the TAB schemeas a mounting scheme. It is obvious that this embodiment can solve theconventional problem that the surface of a sensor is susceptible to oiland moisture from the finger of a person, e.g., a fingerprint. Inaddition, if a photocatalyst such as titania is added to a fluoroplasticfilm, a further improvement in cleanliness and removal of residualfingerprints can be effectively attained owing to the antibacterialaction and fat splitting effect.

[0057] [Second Embodiment]

[0058] Another embodiment of the present invention will be describednext.

[0059]FIG. 3 schematically shows the structure of a surface shaperecognition sensor according to this embodiment.

[0060] In the surface shape recognition sensor shown in FIG. 3, aninsulating protective film 313 serving as a capacitance film formed on asensor electrode 111 is made of silicon nitride, and a surfaceprotective film 314 is made of polybenzoxazole. The insulatingprotective film 313 and surface protective film 314 in FIG. 3 areidentical to those in FIG. 1C, and hence a description thereof will beomitted.

[0061] Assume that residues such as fingerprint residues left on thedetection surface of the surface shape recognition sensor which adetection target touches are sebum. In this embodiment, since apolybenzoxazole film absorbs sebum, almost no fingerprint residues areleft on the surface protective film 314. Polybenzoxazole also has ahydrophobic property (water repellency) so water-soluble foreignsubstances do not easily remain on the detection surface. Therefore, inthis embodiment as well, the tamper resistance improves. Since a filmhaving a thickness enough to fill the space between ground electrodes112 can be easily formed by using a polybenzoxazole film, such a filmcan be formed as an insulating protective film 413, and its uppersurface can be used as a surface protective film, as shown in FIG. 4. Inthis case, it can be said that the insulating protective film 413 isobtained by integrally forming the insulating protective film 313 andsurface protective film 314 in FIG. 3.

[0062] [Third Embodiment]

[0063] As described above, a fluoroplastic film made of a fluorocarbonmaterial can also be formed on the surface of a surface shaperecognition sensor having no ground electrode. Even in a surface shaperecognition sensor having no ground electrode as shown in FIG. 5B, abump 610 serving as an external connection terminal is formed on anouter peripheral portion of the sensor chip, as shown in FIG. 6. In thiscase as well, as described above, if a surface protective film made of afluorocarbon material, i.e., a fluoroplastic film, is formed by coatingthe chip with a coating solution in which a fluorocarbon material thatforms a film having a hydrophobic property is dissolved, the formationof a surface protective film on the external connection terminal (bump610) is suppressed.

[0064] This mechanism will be described in more detail below.

[0065] As shown in FIG. 5A, in a surface shape recognition sensor, amultilevel interconnection layer 502 is formed on a semiconductorsubstrate 501 made of, for example, silicon, and a sensor electrode 507made of aluminum is formed on the multilevel interconnection layer 502through an interconnection 504 and connection electrode 505.

[0066] The uppermost layer of the multilevel interconnection layer 502is covered with an insulating film 503. The interconnection 504 isformed on the insulating film 503. The interconnection 504 is coveredwith an interlayer dielectric film 506 and connected to the sensorelectrode 507 through the connection electrode 505 extending through thethrough hole formed in a portion of the interlayer dielectric film 506.The multilevel interconnection layer 502 is formed from a plurality ofelements such as MOS transistors and a plurality of interconnectionswhich connect them to each other, and forms a sensor circuit and thelike. The sensor electrode 507 is connected to these circuits throughthe interconnection 504 and connection electrode 505.

[0067] The sensor electrode 507 is formed by forming an aluminum filmhaving a thickness of about 0.5 μm on the entire surface of theinterlayer dielectric film 506 by sputtering after the formation of theconnection electrode 505, and processing the film by a knownphotolithographic technique and etching technique.

[0068] After the sensor electrode 507 is formed in this manner, as shownin FIG. 5B, an insulating protective film 508 serving as a capacitancefilm is formed on the interlayer dielectric film 506 so as to cover thesensor electrode 507. For example, the insulating protective film 508can be formed by forming a polyimide film made of a polyimide materialincluded in CRC-8300 series available from SUMITOMO BAKELITE to athickness of about 1 μm by a coating technique and setting the film byheating it at about 300° C.

[0069] A fluoroplastic film 509 made of a fluorocarbon material is thenformed on the insulating protective film 508 (FIG. 5C). A method offorming the fluoroplastic film 509 will be described below. First ofall, AF 1600 is dissolved in Fluorinert FC-75 (solvent) available from3M to form a saturated solution of AF 1600 at a room temperature of23.5° C. This saturated solution will be referred to as a Teflon®saturated solution hereinafter.

[0070] When a saturated solution is formed in the above manner, thissaturated solution is applied onto the insulating protective film 508 byspin coating. The resultant structure is heated in an atmosphere at 170°C. for 5 min. The resultant structure is then annealed in a nitrogenatmosphere at 300° C. for 1 hr. As a result, the fluoroplastic film 509can be formed, as shown in FIG. 5C.

[0071] In addition, an external connection electrode 607 is formed in apredetermined region such as an outer peripheral portion of the chip soas to be connected, through a connection electrode 605, to aninterconnection 604 connected to one of the circuits formed on themultilevel interconnection layer 502. The bump 610 made of gold isformed on the external connection electrode 607. In these regions aswell, the fluoroplastic film 509 is formed on the insulating protectivefilm 508. In contrast to this, as described above, almost nofluoroplastic film is formed on the bump 610.

[0072] Note that a plurality of sensor chips (surface shape recognitionsensors) are simultaneously formed on the semiconductor substrate 501serving as a semiconductor wafer, a detection surface constituted by aplurality of sensor electrodes 507 is formed on each sensor chip, andeach detection surface is protected by the insulating protective film508 and fluoroplastic film 509. FIG. 5C shows part of this structure.

[0073] As described above, only a thin Teflon® film exhibiting pooradhesion can be formed on gold. Even if, therefore, the fluoroplasticfilm 509 is formed by spin coating, almost no film is formed on the bump610. For example, a Teflon® solution obtained by diluting a Teflon®saturated solution at a mixing ratio of 1:1 is applied, by spin coatingat 1,000 rpm, to a wafer on which a plurality of sensor chips, on eachof which components up to the insulating protective film 508 are formed,are simultaneously formed. The resultant structure is heated in anatmosphere at 170° C. and annealed in a nitrogen atmosphere at 300° C.for 30 min to form Teflon® films (fluoroplastic films 509).

[0074] As a result, a Teflon® film having a thickness of about 200 to300 nm is formed, with good adhesion, on the insulating protective film508 on which a plurality of sensor electrodes 507 are arranged, butalmost no Teflon® film is formed on the bump 610. Even if a Teflon® filmis formed on the bump 610, the film thickness is about 10 nm asindicated by Table 1 and the film is likely to peel off.

[0075] Even if, therefore, the fluoroplastic film 509 is formed byapplying a Teflon® solution by spin coating, the fluoroplastic film 509on the bump 610 need not be removed separately, and each sensor chip canbe mounted on the mount substrate with electric connection beingestablished. As shown in FIG. 7, a plurality of external connectionelectrodes 607 and bumps 610 are formed on the outer peripheral portionof a detection region 701 in which the plurality of sensor electrodes ofsurface shape recognition sensors are arranged.

[0076] As has been described above, a surface shape recognition sensoraccording to the present invention includes a surface protective filmwhich has a hydrophobic property and is formed on the surface of aninsulating protective film covering a sensor electrode. This structureprevents substances existing on a detection target from remaining on thesurface of the surface protective film after contact of the detectiontarget with the surface protective film. According to the presentinvention, therefore, a surface shape recognition sensor such as afingerprint sensor used for authentication or the like acquiresexcellent effects. For example, it can suppress a deterioration incleanliness on the detection surface due to residues such as fingerprintresidues left on the detection surface which a detection target such asa finger touches, improve the tamper resistance, and suppress adeterioration in detection precision with respect to a surface shapesuch as a fingerprint.

[0077] In addition, in the method of manufacturing a surface shaperecognition sensor according to the present invention, after aconnection terminal that is exposed on the surface of an insulatingprotective film is formed, a surface protective film made of a specificmaterial is formed on the insulating protective film by coating it witha coating solution in which a specific material such as a fluorocarbonmaterial that forms a film having a hydrophobic property is dissolved.This makes it possible to prevent a surface protective film from beingeasily formed on the upper surface (exposed surface) of a connectionterminal made of, for example, gold.

What is claimed is:
 1. A surface shape recognition sensor comprising: aplurality of sensor electrodes arranged in the same plane on a substrateso as to be insulated/isolated from each other; an insulating protectivefilm which is made of an insulator and formed to cover said sensorelectrodes; capacitance detection means for detecting a capacitanceformed by said sensor electrode; a surface protective film which has ahydrophobic property and is formed on said insulating protective film;and a ground electrode which is formed on the substrate such that saidground electrode is partly exposed on surfaces of said insulatingprotective film and said surface protective film so as to beinsulated/isolated from said sensor electrode and come into contact witha surface of a detection target, wherein said capacitance detectionmeans is configured to detect a capacitance between said groundelectrode and each of said sensor electrodes.
 2. A sensor according toclaim 1, wherein said surface protective film has a lipophobic property.3. A sensor according to claim 2, wherein said surface protective filmpeels off by a thickness on the molecular level upon contact of adetection target.
 4. A sensor according to claim 2, wherein said surfaceprotective film is made of fluorocarbon.
 5. A sensor according to claim1, wherein said surface protective film is made of polybenzoxazole.
 6. Asensor according to claim 5, wherein said insulating protective film andsaid surface protective film are integrally formed.
 7. A sensoraccording to claim 1, further comprising: a detection surface which isformed from said plurality of sensor electrodes and covered with saidinsulating protective film and said surface protective film; and anexternal connection terminal formed from a bump structure which isformed on a portion of the substrate which is located around thedetection surface and protrudes from an upper surface of said surfaceprotective film.
 8. A method of manufacturing a surface shaperecognition sensor including at least a plurality of sensor electrodesarranged in the same plane on a substrate so as to be insulated/isolatedfrom each other, an insulating protective film which is made of aninsulator and formed to cover the sensor electrodes, capacitancedetection means for detecting a capacitance formed by the sensorelectrode, and a connection terminal exposed on a surface of theinsulating protective film, comprising: the step of forming a surfaceprotective film made of a specific material, which forms a film having ahydrophobic property, on the insulating protective film by coating thefilm with a coating solution in which the specific material isdissolved.
 9. A method according to claim 8, wherein the surfaceprotective film has a lipophobic property.
 10. A method according toclaim 9, wherein the surface protective film peels off by a thickness onthe molecular level upon contact of a detection target.
 11. A methodaccording to claim 9, wherein the specific material is made offluorocarbon.
 12. A method according to claim 8, wherein the surfaceprotective film is made of polybenzoxazole.
 13. A method according toclaim 8, wherein the connection terminal is a ground electrode which isformed on the substrate such that the ground electrode is partly exposedon surfaces of the insulating protective film and the surface protectivefilm so as to be insulated/isolated from the sensor electrode and comeinto contact with a surface of a detection target.
 14. A methodaccording to claim 8, wherein: the connection terminal is an externalconnection terminal formed from a bump structure which is formed on aportion of the substrate which is located around a detection surfaceformed from the plurality of sensor electrodes and covered with theinsulating protective film and the surface protective film so as toprotrude from an upper surface of the surface protective film; and themethod further comprises the mounting step of connecting the externalconnection terminal to a connection portion formed on another substrateby an eutectic reaction after the insulating protective film is formed.15. A method according to claim 14, wherein in the mounting step, theexternal connection terminal is connected to the connection portion by aTAB scheme.